VFD Motors...

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giri Power-User Join Date: May 2009 Location: Some where on Earth !!!. Posts: 243 Good Answers: 2	VFD Motors... 10/31/2016 12:21 AM
	What I understand from my experience so far is that the VFD driven motor are different from standard motors by 2 ways. 1) They undergo VPI(vacuum pressure impregnation 2)They will have insulated bearing in NDE side. Is there any other difference between standard & VFD motor such as size?. Kindly share your knowledge. Thanks. __________________ "Know something about everything and everything about something"
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lyn Guru Join Date: Oct 2008 Posts: 42355 Good Answers: 1693	#1 Re: VFD motors... 10/31/2016 12:38 AM
	what is the difference between ordinary electric motor and a VFD ... General Purpose vs Inverter Duty - Motors from AutomationDirect When Should Inverter-Duty Motors Be Specified? - Department of ... CR4 - Thread: Inverter Duty vs Conventional AC Induction Motors
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Crabtree Guru Join Date: Jul 2007 Location: Commissariat de Police, Nouvions, occupied France, 1942. Posts: 2599 Good Answers: 77	#2 Re: VFD motors... 10/31/2016 9:51 AM
	In addition to that, you need to be aware that a motor connected to a VFD has the potential to emit more heat, and therefore operate at a higher temperature. In zone 1 and zone 2 hazardous areas, this characteristic has implications on Eex d systems in that the motor and VSD need to be selected as a combination as opposed to individual items. In most cases the implication is to go up one size on the motor to keep its casing within the T rating. In all cases, seek advice from both the VFD's and the motor's manufacturers. __________________ Good moaning!
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JRaef Guru Join Date: Sep 2006 Location: California, USA, where the Godless live next door to God. Posts: 4665 Good Answers: 804	#3 Re: VFD motors... 10/31/2016 10:31 AM
	There is no enforceable 3rd party standard defining a "VFD motor" or "Inverter Duty" motor, so it still boils down to "let the buyer beware". There are voluntary design standards, but they are performance based, meaning how a manufacturer gets there is their own business. So some may use vacuum impregnating, others don't. Some include isolating bearings (both ends by the way), others include shaft grounding, some ignore the bearings altogether. Some use 1600V winding insulation, others use 2000V, some use 2200V. Some use fish paper in the slots, others don't. Some do nothing more than de-rate one size and call it good! In general, you get what you pay for. The advice I always give is to read the specifications on what you are buying and study up to understand what they mean to you. __________________ All I every really wanted to be, was... A LUMBERJACK!.
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Tornado Guru Join Date: May 2009 Location: Richland, WA, USA Posts: 21017 Good Answers: 795	#4 Re: VFD Motors... 10/31/2016 5:09 PM
	An example of a manufacturers' standard would be NEMA MG-1, which may give you some guidance. __________________ In vino veritas; in cervisia carmen; in aqua E. coli.
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dhayanandhan Guru Join Date: May 2008 Location: CHENNAI, TAMIL NADU, INDIA. Posts: 1851 Good Answers: 65	#5 Re: VFD Motors... 10/31/2016 10:42 PM
	Dear Mr. Giri, The following are also differenc for VFD motors. 1. A seperate air blower with filter to cool the motor - irrespective of speed which may vary from 10% to 90% during operations. The normal motor for small or medium size - which run near to synchronous speed will have a shaft mounted fan. 2. Bearing Insulation is also followed which is economical as the Insulated Bearing is costly/expensive. 3. The earthing - flat AREA should be 2.5 times more than the conventional motor earth flat area of same capacity motor. 4. The earthing should be dedicated one - that is independent and other motr/equipment earthing should not be clubbed. DHAYANANDHAN.S
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rwilliams Guru Join Date: Jul 2016 Posts: 1367 Good Answers: 105	#6 Re: VFD Motors... 11/01/2016 8:22 AM
	In practice, (my continuous experience in industrial equipment for past 25 years now), any energy efficient motor will work fine down to a 10 to 1 turn down, 6 Hertz, and pretty much any rag-tag collection of NEMA Design B and metric integral hp motors will work down to a 6 to 1 turn down, with normal expected life. There will be outliers, where the mechanical load is consistently equal to the motor rating, it will get hot at the lower speeds, for constant torque loads. In practice, for ratings at least through 150hp, it is unnecessary to purchase special designs for a motor, unless it gives you peace of mind. (modern IGBT PWM drives are very kind to motors these days)
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Crabtree (1); dhayanandhan (1); JRaef (1); lyn (1); rwilliams (1); Tornado (1)

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